Salt bath furnace



Inventor; Ferdinand Brie H15 Attorney.

F. BRIEGER SALT BATH FURNACE Filed April 12. 1939 sept. 17, 1940.

Patented Sept. 17, 1940 PATENT OFFICE SALT BATH FURNACE Ferdinand Brieger, Berlin-Kopenick, Germany,

assigner to General Electric Company, a corporation of New York Application April 12,1939, Serial No. 267,507 In Germany June 10, 1938 2 Claims.

My invention relates to salt bath furnaces and its object is to provide an improved Construction or such furnaces which will facilitate the neat treatment of worktherein, will enable the use of a furnace of relatively small dimensions, and will be effective in reducing the deterioration of the furnace Crucible.

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended Claims.

In the single figure of the drawing which illustrates a preferred embodiment of my invention, l is a metal Crucible containing the salt bath 2 and having the backing 3 of heat insulating material. immersed in the salt bath are the two electrodes 4, 4, which are connected, by means not shown, with any suitable source of current supply. When a metal Crucible is used in such a furnace the current supplied to the electrodes divides within the furnace, one part traversing the bath and the work to be treated therein, and the other part traversing the bath and the crucible. It is well known that a metal Crucible deteriorates more or less rapidly by reason of said `other part of the current and that such deterioration is dependent upon the amount of such current. It is therefore desirable to reduce that part of the Current which flows by way of the crucible between the two electrodes. In the past this has been prevented by spacing the electrodes a considerable distance from the walls of the Crucible to insure that only a small part of the current between the electrodes flowed through the crucible. As a result of such spacing of the electrodes from the Crucible the available space for work was greatly reduced. Moreover, when no work was present in the bath the full current supplied the electrodes passed to and from the crucible,

In accordance with my' invention, I have pre vided the metal work holding receptacle 5 which is shown having the lifting lug 6 and having numerous openings 'l to facilitate the free flow of the bath therethrough to the work, not Shown, held in the receptacle. The receptacle being metallic provides a relatively low resistance path between the electrodes which therefore may be arranged closer than otherwise to the walls of the Crucible. Moreover, the resistance to the flow of current between the electrodes by way of the receptacle is not affected by the amount of work being treated for the receptacle may even be empty. I prefer to construct the receptacle such that the resistance of that current path between the electrodes including the receptacle is materially less than the resistance of the current path between the electrodes including the crucible. This is accomplished by making the aggregate spacing between the nearest portions of the receptacle and the electrodes materially less than the aggregate spacing between the nearest portions of the Crucible and the electrodes. For this purpose I prefer to provide the receptacle with the projecting portions 8 so that the Current flow between the electrodes and the receptacle is Conccntrated to a relatively small area where the greatest heating of the bath occurs and hence causes a rapid circulation thereof. Thus at each side of the furnace the distance marked a be- L tween the receptacle and the electrodes is materially less than the distance b between the crucible and the electrodes.

I have chosen the particular embodiment described above as illustrative of my invention and it will be apparent that various modifications may be made without departing from the spirit and scope of my invention which modifications I aim to cover by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A salt bath furnace comprising a metal crucible containing the salt bath, a metal work receptacle immersed in said bath, a plurality of electrodes immersed in said bath outside of said receptacle, the aggregate spacing ofthe electrodes from the nearest portions of the receptacle being materially less than that of the electrodes from the nearest portions of the Crucible.

2. A salt bath furnace Comprising a metal Crucible containing the salt bath, a plurality of elec- L in spaced from the crucible and a removable receptacle immersed in the bath, said receptacle having projections thereon extending toward the electrodes the aggregate distance between the electrodes and said projections being materially less than the aggregate distance between the electrodes and the Crucible.

v Tweak.

FERDINAND BRIEGER. 

